1. Field of the Invention
The present invention relates to a video encoding/decoding apparatus for color images, and more particularly, to an apparatus and method for performing optimal encoding/decoding on a basis of color information and resolution information of color images.
2. Description of the Related Art
A conventional video compression method converts an image format such as an R-G-B image into an image format such as a Y-Cb-Cr image suitable to compression, to obtain a high compression rate. Also, the conventional video compression method reduces chroma (Cb, Cr) components to ¼ of their original sizes and encodes the Cb and Cr components to enhance compression efficiency. However, the conventional video compression method is not suitable for applications requiring high-quality image restoration because energy loss is generated due to subsampling of the Cb and Cr components and the quality loss of the corresponding image which is generated when R-G-B components are converted into Y-Cb-Cr components. To reduce these losses, it is necessary to encode the Cb and Cr components with the same resolution as the Y components.
Also, to obtain better quality when encoding the Y-Cb-Cr components, it is necessary to reduce the quality loss of the image by directly encoding the R-G-B components. However, the conventional video compression method encodes the R-G-B components using a conventional Y-Cb-Cr encoder without utilizing characteristics existing in the R-G-B color components different from those of Y-Cb-Cr components. A representative example of such a conventional video compression method is the AVC/H. 264 standard developed by the Joint Video Team of the ISO/IEC MPEG and ITU-TVCEG.
However, since an R-G-B component and a Y-Cb-Cr component have different image characteristics, encoding efficiency is very low if the R-G-B component is encoded by the conventional Y-Cb-Cr encoder. For example, the respective components (Y, Cb, and Cr) of a Y-Cb-Cr image have no correlation within a same area, while the respective components (R, G, and B) of an R-G-B image have correlation within the same area.
Also, the R, G and B components of the R-G-B image have a similar frequency characteristic, however, in the Y-Cb-Cr image, the Y component has a Luma component that is different from a frequency characteristic of Cb and Cr components having Chroma components due to a process performed when the R-G-B image is converted into the Y-Cb-Cr image. As such, the conventional video compression method has not correctly reflected characteristics of the R-G-B image and the Y-Cb-Cr image with respect to encoding. Also, the conventional video compression method has not reflected the change of the frequency characteristic according to the size of an image when encoding.